There are informal, semi-formal and formal methods in software specification. Among them, formal method which is based on mathematical theory had been used to remove ambiguity, incompleteness and contradiction efficiently. In this paper, we propose implementation steps from Z specification to EJB source code, Also, as a case study we show steps consisted of specifying stack data structure and implementing it in EJB. In conclusion, Z specification proved to be capable of implementing EJB interface, exception class, method, through refinement and definition of schema, interface, post-condition, pre-condition.